The high temperatures of gases and components within gas turbine engines require advanced cooling solutions. In the “hot sections” of a gas turbine engine, the walls of some components can be exposed to gases having temperatures above the melting point of the material used to form the walls. As a result, the walls of such components can contain a number of cavities through which cooling air flows to reduce component temperature.
Dual wall gas turbine engine components offer improved cooling compared to single wall components. For example, a single wall airfoil typically includes a pair of outer walls spaced from one another by a main cavity (or set of cavities). Cooling air flows through the main cavity to cool the inner surfaces of the outer walls and/or to facilitate impingement cooling of the airfoil. Typically, dual wall components include both outer and inner walls. One cavity (sometimes referred to as a “skin cavity”) is positioned between an outer wall and an inner wall and another cavity (a central cavity) is positioned between the inner wall and another inner or outer wall. Cooling air flows through the central cavity to cool the inner surfaces of the inner wall and/or to facilitate impingement cooling of the airfoil. Cooling air flows through the skin cavity to cool the inner surfaces of the inner wall and outer wall and/or to facilitate impingement cooling of the airfoil.
While dual wall components offer the potential for improved cooling, these components are generally difficult and expensive to manufacture. Currently, dual wall components are generally cast using ceramic cores and/or refractory metal cores (RMCs). Investment casting is generally used to form dual wall components, in which one or more ceramic cores are used to form the central cavity or cavities and either ceramic cores or RMCs are used to form the skin cavities. The use of ceramic and RMCs offer disadvantages due to core deformation. As a result of core deformation, greater design tolerances must be built in to the manufacture of dual wall components.